The problem of circular saw kick back induced by a saw blade binding in the saw kerf is well known. In modern high speed and high power low weight hand-held circular saws, the resulting kick back can be extremely violent, and it is not uncommon for the operator to lose control of the saw and be injured.
Numerous attempts to minimize the problem have been made. For example, friction clutches have been utilized in the ouput spindle or gear drive. Friction clutches have the disadvantage of requiring constant adjustment, and to be effective must limit to power output of the saw. In heavy cutting, they are prone to slipping and overheating.
Another approach is to utilize a "dead man" type brake which is applied when the operator loses his grip on the saw. This type of mechanism to be effective must be fast operating, and the entire inertia of the drive as well as the output power of the tool must be absorbed by the brake. This approach in many cases resulted in cumbersome mechanisms which detract from operator grip and control of the device and the severe braking required to be effective is damaging to the power drive of the tool.